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Patented Aug. l6, I898.

W. BEER.

CONSTRUCTION OF METAL BRIDGES.

(Application filed Sept. 22, 1897.)

2 Sheets-Sheet 11.

(No Model.)

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No. 609,001. Patented Aug. 16, I898. W. BEER.

CONSTRUCTION OF METAL BRIDGES.

(Application med Sept. 22, 1897.) (Ila Model.) 2 Sheets-Shaet 2.

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WALTER BEER, on LoND-o ENGLAND.

CQNSTRUCTION ,OF METAL BRIDGES.

SPECIFICATION forming part of Letters Patent No. 699,001, dated August16, 1898. Application filed September 22, 1897. Serial No. 652,601. (Nomodel.) Patented in Ilngland November 12, 1896.110. 25,4:21.

To all whom it may concern:

Be it known that I, WALTER BEER, a subject of the Queen of Great Britainand Ireland, and a resident of London, England, have invented new anduseful Improvements in the Construction of Metal Bridges, (for which Ihave received a patent in Great Britain, hearing date November 12, 1896,and numbered 25,421,) of which the following is a specification.

My said invention relates to improvements in the construction of metalbridges of the well-known double or balanced cantaliverandcentral-girder type. Hitherto the central-portion of such bridges hasbeen spanned by some form of girder or structure having practically onlyvertical reactions. Such structures impose very severe loads upon thesupportingcantalivers. The object of my invention is to reduce theseverity of this loading, and this I efiect by substituting for thecentral girder which spans the space between the projecting double orbalanced cantalivers any suitable form of arch,whereby I obtain obliquereactions or thrusts instead of the ordinary vertical reactions. Thearch is of metal of any suitable section, and the central portion of theplatform or floor of the bridge is supported by the arch, which abutsagainst the cantalivers.

In order that my invention may be clearly understood, I have annexed tothis specification illustrative diagrams and drawings.

Figure 1 represents, diagrammatically, an ordinary double or balancedcantaliver and central-girder bridge. A A represent the cantaliversresting upon their piers or abutments B B. 0 represents the ordinarygirder which spans the gap between the two cantalivers A A and iscarried by them. It will be seen that the girder, together with itsload, bears vertically upon the projecting ends of the cantalivers andproduces vertical reactions R R, as indicated by the arrows g g. Thetendency of the downward pressure from the girder O on the ends of thedouble cantalivers is to raise the other end of each cantaliver in thedirection of the arrows marked w. The severity of these reactionsrmay beconveniently measured by their moments about the 'ured by the quantity R1 points of support B B, which moments are respectively represented bythe algebraic quantity R X y.

My invention, as illustrated by Figs. 2 to 5, consists in substitutingfor the central girder hereinbefore described an arch D, abutting on thedouble or balanced cantalivers,tl1ereby attaining oblique reactions R R.The moments of these reactions about the points of support 13 B may bemeasured by the formula R z in the same way that the moments of thereactions from girder C, Fig. 1, were meas- By varying the rise or formof the arch D the directions R may be changed so that they will passbelow the points of support, as in Fig. 2, through these points, as inFig. 3, or above, as in Fig.4... E

In the case ofFig. 2, R ,e may be made considerably less than R y inFig. 1.

In Fig. 3, R z will equal 0, and in Fig. 4. R z will have a negativevalue (it' R ;y in Fig. 1 be taken as positive) and will help to supportany loads upon the cantaliver-arms e e or cause downward reactions at a:m.

Fig. 5 illustrates an application of my invention.

The roadway F is carried on the top of the double or balancedcantalivers A A and sus pended from the arch D. It may be reached bylifts or stairways in a tower, as at T, or by an inclined approach-roador from high ground or by any other convenient means. The arch maysimply abut against the ends of the cantalivers, as shown at m, or itmay be secured by a hinge or by plates, as shown at 'n, or by otherconvenient means.

I claim- A bridge having a pair of double or balanced cantalivers, andan arch located above the plane of the roadway and occupying the spacebetween the ends of the can talivers, the ends 01": the arch abuttingagainst the ends of the cantalivers, substantially as described.

In witness whereof I have hereunto set my hand in presence of twoWitnesses.

v WALTER Witnesses:

WALTER G.GR1BRLE, FRANK H. S. J owns.

